Traditional microscopes are illuminated by a mirror-and-fork arrangement or by a tungsten or halogen bulb built into or attached to the stage. Mirror-and-fork arrangements are often not dependable and require frequent realignment. Tungsten and halogen lamps generate heat and thus have relatively short lives. These illuminators do not allow for adjustment of the light source to ensure that the specimen being examined is well lit, nor are they interchangeable between different microscope models.